Import patches-unapplied version 0.47ubuntu8 to ubuntu/xenial-proposed

Imported using git-ubuntu import.

Changelog parent: 87bbbbd9413d055da1630709152c94b304068069

New changelog entries:
* debian/patches/05_python3.patch: del the indexer instance explicitly
before sys.exit(), so that it gets decrefed and freed before Python's
implicit shutdown machinery can potentially leave an empty os module for
ServerProgress.__del__() to find. (LP: #1530518)